The present invention relates to a method of forming a balloon catheter to be used in a percutaneous transluminal coronary angioplasty (PTCA) procedure and/or in a stent implantation into a patient's body lumen.
A balloon catheter has been widely used for vascularization of a coronary artery. In this case, a balloon attached to a catheter is delivered into a coronary artery to enlarge a stenosis, i.e. constriction in the coronary artery. Since a large pressure is applied to the balloon to enlarge the stenosis, the balloon is required to withstand high inner pressure.
Conventionally, a balloon used for a balloon catheter has been made by blow molding method. When the blow molding method is used, as shown in FIG. 13, a balloon member 102 having a diameter substantially the same as that of an inner tube member 101 is disposed over the inner tube member 101. Then, as shown in FIG. 14, the inner tube member 101 with the balloon member 102 thereon is placed in a mold 104, which includes an inner chamber 105 in a shape of an inflated balloon and heating elements 106.
Thereafter, the mold 104 is heated by the heating elements 106 in the mold 104, and a gas for blowing the balloon member 102 is supplied from the inner tube 101. The balloon member 102 is inflated by the gas supplied from the inner tube 101 and entered inside the balloon member 102 through a communication hole 103 in the inner tube member 101. The balloon member 102 is inflated to abut against the wall portion of the mold 104 as shown in FIG. 15. Then, end portions 107, 108 of the balloon member 102 are adhered to the inner tube member 101 by an adhesive or the like. The end portions 107, 108 of the balloon member 102 may be fixed to the inner tube member 101 before blow molding the balloon member.
In the conventional blow molding method, however, there is a problem. Namely, since the balloon member, which has a shape of a tube member with the small diameter before blow molding, is blown by the gas supplied thereinto to have a shape of the inflated balloon, degree of inflation of the balloon member is different according to the portions of the balloon member, resulting in uneven thickness. Namely, although the thickness of the balloon member before blow molding is substantially constant, the thickness of the inflated balloon member may be partly different. As a result, if high pressure is applied to the balloon member in use, the balloon member may be torn or broken.
Also, in the conventional balloon catheter, the quality of the balloon catheter can be checked only after the balloon member is formed.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of forming a balloon catheter, wherein the high quality balloon catheter can be formed easily at a low cost.
Another object of the invention is to provide a method of forming a balloon catheter as stated above, wherein a balloon portion with a constant thickness can be formed without fail.
Further objects and advantages of the invention will be apparent from the following description of the invention.